Faint yellow dots can barely be seen in this image taken by the Electronic Frontier Foundation

“We didn’t advertise it much to the people that had [the printers],” While technology has clearly advanced since the early age of laser printers, microdots are still very much present — something discovered in a top secret NSA document published by The Intercept earlier this month.

“We didn’t not tell them if they asked. The salespeople were told, ‘Don’t lead with it in any sales, but if they ask you about it, you can tell them we have the security feature in there’.”

While technology has clearly advanced since the early age of laser printers, microdots are still very much present — something discovered in a top secret NSA document published by The Intercept earlier this month.

Unbeknown to the publication at the time, the published document contained a hidden code that identified NSA contractor Reality Winner as the source of the leak.

Security expert Rob Graham explained by downloading the document and inverting the colours in a photo editing program, he was able to reveal a pattern.

When plotted against a grid, these yellow dots denoted specific hours, minutes, dates and numbers.

Thus by reverse-engineering the grid pattern, researchers were able to discover the document had come from a printer with the serial number 535218 or 29535218 — more than enough information to reveal the source.

Funnily enough investigators didn’t need to get so crafty, with an affidavit released by the Department of Justice explaining Winner had actually sent the document to the media outlet from her work email and this is how she was captured.

“The US Government Agency determined that six individuals printed this reporting. Winner was one of these six individuals,” the affidavit read.

“A further audit of the six individuals’ desk computers revealed that Winner had email contact with the News Outlet. The audit did not reveal that any of the other individuals had email contact with the News Outlet.”

While helpful in instances such as this, the yellow dots are also instrumental in helping to expose fraudsters trying to pass a forged document printed in the past six months as something from 2005.

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“The encoding scheme used by snow relies on the fact that spaces and tabs (known as whitespace), when appearing at the end of lines, are invisible when displayed in pretty well all text viewing programs,” he wrote.

“This allows messages to be hidden in ASCII text without affecting the text’s visual representation. And since trailing spaces and tabs occasionally occur naturally, their existence should not be sufficient to immediately alert an observer who stumbles across them.”

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